A water truck and blade add layers of ice chips and water to an ice road near one of ConocoPhillips’ flow lines on the Western North Slope. (Photo by Elizabeth Harball/Alaska’s Energy Desk)Every winter, a massive infrastructure project takes place on the North Slope — one that’s designed to disappear. Ice roads are built to minimize the oil industry’s footprint on the sensitive tundra, and melt away in spring. Many of the oil industry’s multi-million dollar projects on the North Slope can’t be built until the ice roads are finished each year.Listen nowOn a dim, seven-degree day in January, a van slowly lurches down the beginnings of an ice road on Alaska’s North Slope. Jeff Osborne, who oversees ice road construction for ConocoPhillips, said that the ice under the tires is as thin as one or two inches. It’s really bumpy.“You get used to it,” Osborne said.This tour has been arranged (and paid for) by ConocoPhillips. It’s the only way a reporter can see how the oil company operates in this remote part of the state.Here on the North Slope, oil companies like ConocoPhillips build hundreds of miles of ice roads every winter, at a cost of about about $400,000 per mile. Osborne explained there are no permanent roads to the company’s Alpine facility, or to many of the pipelines nearby.An ice chipper moves across a frozen lake, leaving behind material used to build ice roads. (Photo by Elizabeth Harball/Alaska’s Energy Desk)“That’s the amazing part,” Osborne said. “I don’t know anywhere else in the world where you can build pipelines and when we walk away and everything melts, you can look from the road or from afar and you wonder to yourself, ‘how did those pipelines get placed?’”ConocoPhillips’ North Slope work schedule hinges entirely on ice roads. The season lasts 90 to 100 days. During that narrow window, the Alpine workforce doubles in size. Essential equipment like drill rigs, pipes, cranes and chemicals — too big or dangerous to carry in by plane — all have to be moved on ice roads.On a frozen lake near Alpine, a big yellow Cat moves back and forth across the horizon. What’s left behind looks like a freshly-plowed field — only it’s frosty white. Huge backhoes scoop up ice chips and dump them into trucks.Back at the road site, the ice chips are dumped onto ground that’s been pre-packed with snow.“At some point in time the blade will call the water truck up and have the water truck put some water down on the chips that have just been dumped,” Osborne said.After water is sprayed down, Mother Nature takes charge, freezing everything into place. Layer after layer is added until the road is at least six inches thick.And that’s pretty much it.“I’ve always thought that ice roads were an elegantly simple solution to a problem,” Melissa Head said. She’s with Alaska’s Department of Natural Resources. “There really isn’t much that’s complicated about it and that’s the beauty of it.”Head is on a team that manages ice road construction on the North Slope. The main purpose of ice roads, she explains, is to protect the tundra’s sensitive vegetation — some plants native to the region won’t grow back for years if they’re disturbed.Environmental groups have raised concerns about ice roads. Lois Epstein with the Wilderness Society in Anchorage worries about the amount of water it takes to build them.“Where that water comes from, making sure that it doesn’t deplete important lakes, river systems,” Epstein said.But Epstein added her group doesn’t oppose ice roads.“It is true, ice roads are much better than permanent roads, gravel roads, so we do support their use,” Epstein said.This winter, ConocoPhillips begins construction on its Greater Moose’s Tooth 1 drill site. It’s one of the company’s first big developments in the National Petroleum Reserve. ConocoPhillips usually builds about 35 miles of ice roads each winter, but for this $900-million project, they need an additional 80 miles.That means Jeff Osborne is keeping busy. Driving back to Alpine in the van, I have to wonder if ice road building feels like a Sisyphean task. I ask him how he feels about the money, time and effort he puts into something that just melts away in the spring.“Job security,” Osborne said simply.By late April, the ice roads Osborne completed just a few months earlier will fade back into the tundra. And next year, he’ll start all over again.How is climate change affecting ice road construction?To build an ice road, state regulators require the tundra to be frozen to a set depth and temperature. ConocoPhillips’ Jeff Osborne, who has worked on ice roads since 1998, said he hasn’t noticed the impact of rising temperatures on his work, but state data shows a shift has occurred.According Alaska’s Department of Natural Resources, the length of tundra travel seasons decreased between 1970 and 2000.In the 1970s and 1980s, it was common for tundra travel season to begin as early as November. But by the mid-1990s and early 2000s, tundra travel season was commonly beginning in January. In 2003, the state adopted new technology and techniques, like temperature monitoring stations and pre-packing snow over the tundra.As a result, “ice road season has actually increased quite considerably because of the pre-packing techniques and new vehicles that are being used,” Melissa Head of the Alaska Department of Natural Resources’ Northern Oil and Gas Team said. Head said the state is not studying the long-term effects of a changing climate on ice roads, and does not have data proving the shift was due to climate change.“There was a recognition that the off-road travel season was changing and was decreasing, but no one attributed that to any specific thing,” Head said.According to the National Oceanic and Atmospheric Administration average annual temperatures in the Arctic have risen 3.5 C since 1900 and continue to increase at double the rate of the rest of the globe.